Cisco issues network security brown alert

Serious DoS risk

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Cisco warned last night of a potentially devastating flaw affecting a wide range of routers and switches.

The DoS vulnerability rises from a bug in Cisco's core IOS software and could cause vulnerable devices to stop processing inbound packets on receipt of maliciously constructed IPv4 packets. Normal service would be restored only with a manual reboot.

No alarms will be triggered, nor will the router reload to correct itself. Cisco IOS versions 11.x and 12.x prior to 12.3 are affected by the vulnerability. That means almost everybody is affected.

Indications are that there are no exploits for the bug as yet, however that's no reason for complacency. The flaw is just about as serious a security issue with networking equipment as one could imagine.

Cisco has issued an advisory with workarounds and available fixes, which network admins are strongly advised to promptly review. Security clearing house CERT has also issued an advisory on the problem. ®